Electric Kilowatt Hour (kWh) meters are widely used to measure the consumption of energy supplied by a power source(s) via power lines, such as those supplying electrical power to a consumer's home or office. As is known, electrical power is measured in watts (i.e., Joules per second), and for convenience is often measured in kilowatts. Typically, utility companies charge power consumers for kilowatt-hours consumed over time. Where power is the amount of energy per unit of time, a kWh is defined as the amount of work done at a constant rate of one kilowatt for one hour, and is therefore a unit of energy. Electric kWh meters therefore provide an indication of the energy consumed over time, yet are often casually referred to as power meters. These "power" meters are typically employed by electric utility companies in order to charge each consumer for the amount of electrical energy that was consumed over a period of time.
Traditional kWh meters included mechanical rotors connected to numeric display wheels via a set of gears. Periodically, such as every month, a person visually read a number corresponding to the energy consumption that was displayed on the wheels, and forwarded the reading to the electric utility for subsequent billing of the consumer. This type of process was costly, slow, and intrusive to customers.
In order to alleviate some of the problems associated with the traditional approach, other approaches have more recently been employed resulting in the evolution of power/kWh meters into fully-electronic, yet more costly, metering devices. Many of these meters utilize electronic techniques to measure the consumed energy and display the total on electro-optical readouts, and some even have features allowing the measured kWh information to be sent to the electric utility via electronic communication devices using pager and modem technologies. However, in spite of the electronic communication abilities of these electronic meters, the typical electronic kWh meters have had visual readouts on them, which limited the package design and mounting locations for the meters.
In addition to pager, modem and other auxiliary communications techniques, it is also conceivable that the information is transmitted via the power line itself. One particularly advantageous manner for communicating data representing a kWh meter reading is disclosed in U.S. Pat. No. 5,581,229 ('229), commonly assigned to the assignee of the present invention. In the '229 system, a transmitter is mounted in an existing power meter, and is electrically coupled to the power line. A data signal from a kWh meter, representing the amount of energy consumption, is modulated by the transmitter and sent at low frequencies over the power lines to a receiver, which receives and demodulates the transmitted signal to restore and process the original data signal. The unique transmission system described in the '229 patent therefore describes a data transmission system designed for the transfer of information via the power line itself. The information transmission occurs at a lower frequency than the frequency of the power signal being distributed on the power distribution line. Such low frequency control signals allows for longer transmission links, and reduces the chance that the information will interfere with the electrical power transmission. Furthermore, a low frequency signal can pass through transformers and capacitors with minimal signal degradation, and without the aid of additional equipment such as repeaters. As will be described in further detail below, the present invention is particularly beneficial when used in connection with such an information transmission system, or in connection with other communications systems where information is transmitted using the power line as the information transfer medium.
Among electric utilities worldwide, kWh meters are generally available in two common package types. The plug-in meter, referred to as an S-base meter, is popular in North America. This type of meter is plugged into a socket, or meter base, that is typically located on a pole or pedestal, or an outside wall of a building. The A-base meter is popular in much of the rest of the world. The A-base meter is usually connected to the power wires with screw terminal-type connections, and are usually positioned similarly to S-base meters.
Electric kWh metering is important to power utilities to provide fair and efficient service. When metering is not used, consumers can be very wasteful which collectively causes all consumers utility costs to rise. When metering is employed, each consumer pays his or her fair share--at least in theory. For example, when a consumer uses more energy relative to other consumers, that consumer should pay more. However, because KWh meters essentially represent the electric utilities' cash registers, they become a target for graft, corruption and tampering.
Most conventional kWh meters have to be physically viewed to obtain a reading, which means that the meter has to be located such that utility personnel are able to read it. This typically results in the meter being in plain sight of consumers, tempting some to rewire, bypass, slow down, damage or otherwise tamper with the meters. This further tends to make the utility personnel directly accessible to the consumers, which, particularly in developing countries, has presented an entirely different type of chicanery. For example, in many developing countries, it is known that power consumers often convince the utility personnel to "modify" the energy reading using various forms of coersion, bribery and extortion. This significant problem has led to substantial financial losses for the utility companies.
Prior art meters are typically mounted within an electrical box, or on a pole or other rigid structure to which the power line is also secured. These mounting positions also typically make the meter accessible to consumers. For example, a meter mounted in an electrical box within the consumer's home is clearly accessible to the consumer, which eases tampering if the consumer chooses to do so.
In addition to these human-oriented problems, a meter device also has to survive environmental factors such as temperature and humidity extremes, sunlight, bugs, rain, lightning, and physical abuse from animals, weather and humans. The problems surrounding the use of visual meter displays and the need for utility personnel to read the meters are exacerbated by such adverse conditions and events.
Accordingly, there is a need for a metering apparatus and technique that avoids most, if not all, of the above-noted concerns. The present invention minimizes tampering related to the metering and forwarding of energy consumption information, and effectively eliminates the possibility of fraudulent activity resulting from the human element. The present invention therefore overcomes these and other problems of the prior art, and offers a variety of advantages over the prior art.